If there's black elves... why all the orcs are white?

Orcs were supposed to be a race created from Elves corrupted by Sauron, or the previous dark lord before Sauron (I don't remember the name).

The show gives them white skin and makes them look like an extremely corrupted version of Caucasian features, which is perfectly fine if elves were played by Caucasian whites. It makes sense.

However, the show includes black Elves, but it doesn't include the corresponding Orcs. Where are the Orcs that were created from black Elves? Or only white Elves could be corrupted?